A decision by the Federal Reserve to expand its bond buying next week is likely to prompt policy makers to rewrite their 18-month old blueprint for an exit from record monetary stimulus.

Under the exit strategy, the Fed would start selling bonds in mid-2015 in a bid to return its holdings to pre-crisis proportions in two to three years. An accelerated buildup of assets would also mean a faster pace of sales when the time comes to exit -- increasing the risk that a jump in interest rates would crush the economic recovery.